| China is extremely rich in molybdenum resources.The global reserves of molybdenum resources are about 17 million tons(2018),of which nearly half are distributed in China(49%).The Qinling molybdenum ore belt is the second largest molybdenum ore belt in the world after the CHmax-Henderson molybdenum ore belt in the United States.Qiushuwan copper deposit is the largest PORPHYRY-SKARN copper-platinum deposit in the eastern part of Qinling orogenic belt.The alteration zoning is studied by modern remote sensing interpretation method and the genesis of ore bodies is analyzed by geochemical data.It not only provides geological basis for further exploration in Qiushuwan copper deposit,but also has reference significance for other copper deposits in Qinling orogenic belt.On the basis of fully collecting and summarizing the research achievements of predecessors in the East Qinling Mountains,and through field geological survey,regional geological investigation,geological analysis of deposits and structural geological analysis,the paper establishes a plane alteration-mineralization zoning model of Qiushuwan copper-molybdenum deposit by means of remote sensing data interpretation method,and obtains the following understanding through geochemical data analysis of ore body genesis.The Qiushuwan copper-molybdenum deposit is located in the eastern part of the East Qinling orogenic belt.On the northern side of the intersection of the regional Shang-Dan fault and Zhu-Xia fault,porphyry-type and SKARN-TYPE molybdenum orebodies and breccia-type copper orebodies are developed.The molybdenum orebodies mainly occur in Nanshan molybdenum ore section and Xishan ore section,and mainly occur in explosive breccia belt,skarn and skarnized marble.The ore bodies are obviously controlled by skarn-structure.It is located in the inner and outer contact zone between Qiushuwan rock mass and Yanlinggou Formation.Based on remote sensing structural interpretation and alteration zoning interpretation,a planar alteration-mineralization zoning model of Qiushuwan coppermolybdenum deposit is proposed.Outside the Yuantou Mountains,the alteration zones are annular in distribution: silica cap-skarn + sericitization-skarn + sericitization + sericite+qingpan-skarn+qingpan+sericite-skarn+qingpan+qingpan-qingpan;mineralization is also annular in distribution: molybdenum-molybdenum(copper)-copper-lead+zinc+silver.The Re-Os isotopic dating results of Qiushuwan copper-molybdenum deposit in Qiushuwan copper-molybdenum deposit are 147.4±4Ma.Combined with the Re-Os isotopic ages of Jinduicheng,Nannihu,Sandaozhuang and Leimengou deposits,it is considered that a large-scale mineralization occurred in the eastern Qinling Mountains of 140 Ma.The analysis of main and trace elements shows that the Qiushuwan coppermolybdenum ore-forming parent rock-Qiushuwan granite porphyry has the characteristics of high silicon,high aluminium,high Ba,high Sr,alkali-rich,potassiumrich,low magnesium,low calcium,low total rare earth,no obvious Europium anomaly,enrichment of large ion lithophile,low Nb and Ti,and has undergone crust-mantle mixing,which indicates that the area may be in local extension after collision orogeny.The geotectonic environment of action.Based on the evolution of the Qinling orogenic belt,it is considered that the Yangtze plate subducted under the North China plate at the end of the Triassic and cut the mantle,which provided a channel for the later magma uplift.For the extension transition period(± 140 Ma)after the subduction of the Yangtze Plate to the North China Plate,the rapid decompression after the compression caused the crustal extension mantle material upwelling along the deep and large faults,bringing a large number of metal mineralization materials.The Qiushuwan granite porphyry was formed by emplacement of crust-mantle mixed magma along the grid structure intersection of near east-west and near north-south faults.The process of Qiushuwan granite porphyry condensation differentiation,metasomatism and blasting is the process of forming Qiushuwan copper-molybdenum deposit. |
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